Observation of proximities between spin-1/2 and quadrupolar nuclei: Which heteronuclear dipolar recoupling method is preferable?
- UCCS (CNRS-8181), Lille North of France University, Villeneuve d'Ascq 59652 (France)
We have recently shown that the dipolar-mediated heteronuclear multiple-quantum coherence (D-HMQC) method allows observing through-space proximities between spin-1/2 ({sup 1}H, {sup 13}C, {sup 31}P Horizontal-Ellipsis ) and quadrupolar ({sup 23}Na, {sup 27}Al Horizontal-Ellipsis ) nuclei. However, the D-HMQC effectiveness depends on the choice of the heteronuclear dipolar recoupling sequence. Here, we compare the efficiency and the robustness of four rotor-synchronized sequences: the symmetry-based ones, R4{sub 1}{sup 2}R4{sub 1}{sup -2} and its super-cycled version, SR4{sub 1}{sup 2}, and two schemes based on simultaneous amplitude and frequency modulations, denoted SFAM-1 and SFAM-2. For the SFAM methods, we point out efficient recoupling conditions that facilitate their experimental optimization and we introduce analytical expressions for the buildup of D-HMQC signal in the case of an isolated spin pair. We show that the main differences between these four sequences lie in the number of adjustable parameters and in their robustness with respect to chemical shift and homonuclear dipolar interactions. The relative performances of these four recoupling sequences are analyzed using average Hamiltonian theory, numerical simulations, and {sup 27}Al-{l_brace}{sup 31}P{r_brace} D-HMQC experiments on crystalline aluminophosphate.
- OSTI ID:
- 22099058
- Journal Information:
- Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 14 Vol. 137; ISSN JCPSA6; ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ALUMINIUM 27
CARBON 13
CHEMICAL SHIFT
COMPUTERIZED SIMULATION
FREQUENCY MODULATION
HAMILTONIANS
HYDROGEN 1
NUCLEAR MAGNETIC MOMENTS
OPTIMIZATION
PERFORMANCE
PHOSPHORUS 31
QUADRUPOLE MOMENTS
SODIUM 23
SPIN